751 research outputs found
One loop calculations on the Wess-Zumino-Witten anomalous functional at finite temperature
We analyze the finite temperature (T) extension of the Wess-Zumino- Witten
functional, discussed in a previous work, to one loop in chiral perturbation
theory. As a phenomenological application, we calculate finite temperature
corrections to the amplitude of the decay into two photons. This
calculation is performed in three limits : i), ii)the chiral
limit at finite T and iii) ( being the pion mass). The
-corrections tend to vanish in the chiral limit, where only the kaon
contribution remains (although it is exponentially suppressed).Comment: Latex, 13 pages and 3 figures avalaible upon reques
On the Wess-Zumino-Witten anomalous functional at finite temperature
We discuss the finite temperature extension of the anomalous Wess-Zumino
-Witten lagrangian. The finite temperature S^1\times S^3 compactification makes
a structure in disconnected sectors, corresponding to different baryon numbers
appear naturally. The consistency of the anomalous functional is proved for
arbitrary baryon number configurations. The anomalous behavior of the
functional is shown to be consistent with the absence of finite temperature
corrections to chiral anomalies in
QCD, for each baryon number sector.Comment: 16 pages, FT/UCM/9/9
Dimensional Reduction and Quantum-to-Classical Reduction at High Temperatures
We discuss the relation between dimensional reduction in quantum field
theories at finite temperature and a familiar quantum mechanical phenomenon
that quantum effects become negligible at high temperatures. Fermi and Bose
fields are compared in this respect. We show that decoupling of fermions from
the dimensionally reduced theory can be related to the non-existence of
classical statistics for a Fermi field.Comment: 11 pages, REVTeX, revised v. to be published in Phys. Rev. D: some
points made more explici
Decoherence in a Josephson junction qubit
The zero-voltage state of a Josephson junction biased with constant current
consists of a set of metastable quantum energy levels. We probe the spacings of
these levels by using microwave spectroscopy to enhance the escape rate to the
voltage state. The widths of the resonances give a measurement of the coherence
time of the two states involved in the transitions. We observe a decoherence
time shorter than that expected from dissipation alone in resonantly isolated
20 um x 5 um Al/AlOx/Al junctions at 60 mK. The data is well fit by a model
including dephasing effects of both low-frequency current noise and the escape
rate to the continuum voltage states. We discuss implications for quantum
computation using current-biased Josephson junction qubits, including the
minimum number of levels needed in the well to obtain an acceptable error limit
per gate.Comment: 4 pages, 6 figure
Shade alters savanna grass layer structure and function along a gradient of canopy cover:Savanna grasses turnover across the light gradient
Low-Lying States of the Six-Dimensional Fractional Superstring
The fractional superstring Fock space is constructed in terms of
\bZ_4 parafermions and free bosons. The bosonization of the \bZ_4
parafermion theory and the generalized commutation relations satisfied by the
modes of various parafermion fields are reviewed. In this preliminary analysis,
we describe a Fock space which is simply a tensor product of \bZ_4
parafermion and free boson Fock spaces. It is larger than the Lorentz-covariant
Fock space indicated by the fractional superstring partition function. We
derive the form of the fractional superconformal algebra that may be used as
the constraint algebra for the physical states of the FSS. Issues concerning
the associativity, modings and braiding properties of the fractional
superconformal algebra are also discussed. The use of the constraint algebra to
obtain physical state conditions on the spectrum is illustrated by an
application to the massless fermions and bosons of the fractional
superstring. However, we fail to generalize these considerations to the massive
states. This means that the appropriate constraint algebra on the fractional
superstring Fock space remains to be found. Some possible ways of doing this
are discussed.Comment: 69 pages, LaTeX, CLNS 91/112
Induced Parity-Breaking Term at Finite Chemical Potential and Temparature
We exactly calculated the parity-odd term of the effective action induced by
the fermions in 2+1 dimensions at finite chemical potential and finite
temperature. It shows that gauge invariance is still respected. A more gerneral
class of background configurations is considered. The knowledge of the reduced
1+1 determinant is required in order to draw exact conclusions about the gauge
invariance of the parity-odd term in this latter case.Comment: 8 pages, LATEX, no figure
A Quantum-mechanical Approach for Constrained Macromolecular Chains
Many approaches to three-dimensional constrained macromolecular chains at
thermal equilibrium, at about room temperatures, are based upon constrained
Classical Hamiltonian Dynamics (cCHDa). Quantum-mechanical approaches (QMa)
have also been treated by different researchers for decades. QMa address a
fundamental issue (constraints versus the uncertainty principle) and are
versatile: they also yield classical descriptions (which may not coincide with
those from cCHDa, although they may agree for certain relevant quantities).
Open issues include whether QMa have enough practical consequences which differ
from and/or improve those from cCHDa. We shall treat cCHDa briefly and deal
with QMa, by outlining old approaches and focusing on recent ones.Comment: Expands review published in The European Physical Journal (Special
Topics) Vol. 200, pp. 225-258 (2011
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